Spark plugs gap question

[Vasiliy]

Hi everyone.
FSM say correct electrode gap is: 0.8 mm (0.031 in.) For a 1fz-fe.

I have denso ik16 with 1.1 mm
Should I reGap them?

Thanks.

 

[Tachycardic]

Yes, they should all be regapped to 0.8mm.

 

[Kernal]

The Denso IK16 should be an Iridium spark plug (I for Iridium). The original specification in the FSM was for a standard plug.

Installed a couple of set of Denso Iridium Power plugs in the past, no issues, not re-gapped. Recently installed a set of Denso IK16TT (Iridium center electrode, platinum tip side electrode) in a different FZJ80 and again, did not regap.

 

[Kay9Cop]

I also just did the Denso IK16TT and they were gapped .036 out of the box. I re-gapped to .032.

 

[Kernal]

From Denso's website FWIW (I'm not a spark plug expert):

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Should I modify the electrode gap?


DENSO spark plugs are manufactured with a pre-set gap. With nickel plugs, especially with motorcycles, the gap may need adjustment. Always use a special spark plug gapping tool to change the gap. Do not change the gap on platinum, iridium or twin tip spark plugs, as the fine electrodes may get damaged.

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NGK:

3. Gapping fine-wire spark plugs

While most NGK spark plugs are pre-gapped, there are occasions when the gap requires adjustment. Care must be taken to avoid bending or breaking off the fine-wire electrodes. NGK recommends a round wire-style or pin gauge gap tool to measure the gap. If the gap must be adjusted, use a tool that only moves the ground electrode and does not pry between or against the electrodes. NGK also recommends adjusting the gap no more than +/- 0.008” from the factory preset gap.


NGK's NZ web site:

Electrode Gap Adjustment - NGK Spark Plugs New Zealand | Iridium Spark Plugs | Glow Plugs | Oxygen Sensors | Ignition Leads | Ignition Coils | EGT Sensors

With over 80 years of experience in Spark Plug manufacturing, NGK are world leaders in spark plug technology. Don't just ask for a spark plug, insist on NGK.

www.ngkspark.co.nz

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And here's one guy's opinion:

NGK Iridium Spark Plug Gap - What will happen? How long will it last?

Want to know if you should Gap NGK Iridium spark plugs? Want to know what is the recommended spark plug gap? Read the answers in this article!

customrigsmag.com

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FWIW, I've been running Denso Iridium plugs as they came out of the box (not regapped) for 20 years and got 16.5 mpg (hwy) out of a stock 96 FZJ80 for the first 150,000 miles on Denso Iridium plugs.

SPARK PLUG

DENSO spark plugs use iridium alloy for their center electrode. Because of its extremely narrow diameter of just 0.4 mm, engine output and acceleration response are greatly improved.

www.denso.com

 

[Tachycardic]

I'm surprised that you wouldn't go with the FSM's recommendation. But, I'm also under the impression that you should go with the gap as specified by the car manufacturer regardless of spark plug material. I could be wrong here, but it also seems to me that from their wording, Denso is more afraid that one will damage the fine electrode while re-gapping. It is fortunate that the OP has a larger gap. It's easier to reduce the gap than it is to increase it.

Still, 16.5mpg is pretty impressive--one of these days I'll have to compare a set of gapped iridiums vs ungapped ones.

 

[Kernal]

It's my impression from reading Denso's literature that it takes less energy
to fire an Iridium plug compared to a standard plug. So my reasoning was
that Denso determined the gap to optimal for that particular Iridium plug and if my aging system could produce enough energy to fire standard plugs at the FSM gap, then it should be able to fire the Iridium plugs at a slightly wider gap.

Either way, I've ran one set of Denso Iridium Power plugs for about 100,000 miles and when I took them out they were in not so bad a shape, center electrode still present, side electrode worn with increased gap. In a pinch they could have been cleaned up, regapped (carefully) and put back in service.

Now on a second set of the same plug with 75,000 miles. Feels like power has dropped off a bit in the low end more recently, but that could be a few other factors including the distributor cap and rotor which are also at 75,000 miles, so can't blame it on the plugs (this particular engine has close to 290,000 miles on it, head untouched).

Also have a set of Denso Iridium TT plugs recently installed into another FZJ80, not re-gapped, no issues.

Not an expert, just figured Denso knows more about their Iridium plugs than I do so decided not to mess with their factory gap. FWIW.

 

[thatcabledude]

Are you even supposed to gap a iridium plug? The electrode is tiny.

 

[Kay9Cop]

Are you even supposed to gap a iridium plug? The electrode is tiny.

Use the tool that bends the side electrode. It never touches the platinum or iridium.

 

[Tachycardic]

It's my impression from reading Denso's literature that it takes less energy
to fire an Iridium plug compared to a standard plug. So my reasoning was
that Denso determined the gap to optimal for that particular Iridium plug and if my aging system could produce enough energy to fire standard plugs at the FSM gap, then it should be able to fire the Iridium plugs at a slightly wider gap.

Either way, I've ran one set of Denso Iridium Power plugs for about 100,000 miles and when I took them out they were in not so bad a shape, center electrode still present, side electrode worn with increased gap. In a pinch they could have been cleaned up, regapped (carefully) and put back in service.

Now on a second set of the same plug with 75,000 miles. Feels like power has dropped off a bit in the low end more recently, but that could be a few other factors including the distributor cap and rotor which are also at 75,000 miles, so can't blame it on the plugs (this particular engine has close to 290,000 miles on it, head untouched).

Also have a set of Denso Iridium TT plugs recently installed into another FZJ80, not re-gapped, no issues.

Not an expert, just figured Denso knows more about their Iridium plugs than I do so decided not to mess with their factory gap. FWIW.

I totally understand that Denso is the expert here on their plugs, but they didn't design the 1FZ-FE, nor did they dictate operating parameters of their IK16 with this engine. I feel that any pre-gapped spark plug was designed to work okay in a variety of engines, but for optimal performance, they should be gapped to what the engine manufacturer states. I don't know--I could be wrong. But, I would seriously consider re-gapping your 75K iridium plugs and see if you get that performance back. It could be that the electrode is wearing and the gap has widened leading to lower performance. Would love to hear if it makes a difference!

 

[Kernal]

The slight fall off in power on acceleration from a stop only happened more recently, otherwise it runs very well, good power. Just got back from a drive in rush hour traffic, zero issues. Need to replace the distributor cap and rotor, check the air filter, maybe toss some cleaner into the intake and tank before I blame it on the stock gapped iridium plugs with 75,000 miles on them. LIkely just time to clean things up, replace cap and rotor, and check a plug or two to
see how they're wearing.

 

[jonheld]

The size of the air gap should be determined by the voltage output of the coil, regardless of plug type. Those pesky laws of physics keep getting in the way of marketing.
There is likely no benefit to running any other plug in these engines. This stuff was all designed in the 1980s.